Toluic acid

ABSTRACT

Process for oxidatively carbonylating toluene to toluic acid, at least 50 mol % of the toluic acid being the p-isomer, said process comprising contacting and reacting, at 110°-250° C., at a pressure of at least 500 psi (3.45 MPa), toluene, carbon monoxide, oxygen and the catalyst ingredients consisting essentially of 
     (a) a compound of rhodium or iridium; 
     (b) a sulfur oxy-acid or a Group Ia or IIa metal salt of a sulfur oxy-acid; 
     (c) a sulfur oxy-acid or sulfur oxy-acid mixture having a Hammett acidity value (-H o ) of greater than 7.0; and 
     (d) a cupric salt of a sulfur oxy-acid; 
     said catalyst ingredients containing 0.3-30 mol % of (a) and 70-99.7 mol % of (b+c+d), with the molar ratios (b/a) and (c/a) each being at least 2 and the molar ratio (d/a) being at least 0.5, and recovering toluic acid.

CROSS-REFERENCE TO RELATED APPLICATION

This is a division of application Ser. No. 328,843 filed Dec. 9, 1981and now U.S. Pat. No. 4,431,839.

DESCRIPTION

1. Technical Field

This invention relates to the oxidative carbonylation of aromaticcompounds, for example, the preparation of toluic acids from toluene,carbon monoxide and oxygen.

2. Background

The oxidative carbonylation of aromatic compounds to aromatic carboxylicacids is known in the art. U.S. Pat. No. 3,700,729 discloses thecatalytic liquid phase process comprising contacting an aromaticcompound and carbon monoxide in a substantially anhydrous organic liquidreaction medium which is inert to the reactants and the catalyst whichis a halide salt of a Group VIII metal in its highest oxidation state,continuing the contacting until the catalyst is reduced to a lowervalence state and the aromatic compound is oxidatively carbonylated, andthereafter hydrolyzing the carbonylated compound to the aromaticcarboxylic acid. The patent exemplifies the conversion of toluene top-toluic acid. U.S. Pat. No. 3,920,734 discloses a process for preparingan aromatic carboxylic acid from an aromatic compound by means of carbonmonoxide, oxygen and a palladium carboxylate catalyst. The patentexemplifies the conversion of toluene to a mixture of toluic acidisomers. U.S. Pat. No. 4,093,647 discloses a process for preparing anaromatic carboxylic acid from an aromatic compound of the benzene seriesby means of carbon monoxide and an inorganic salt mixture consisting ofa major amount of a thallium salt and a minor amount of a palladiumsalt. The patent exemplifies the formation of a mixture of toluic acidisomers, predominantly the p-isomer, from toluene.

The acid-catalyzed carbonylation of aromatic compounds to form aldehydesalso is known in the art. Chem Systems, Inc., Process Evaluation andResearch Planning Report, 2nd quarter, 1976, discloses the HF/BF₃catalyzed carbonylation of toluene to tolualdehyde which can beconverted to terephthalic acid by a liquid phase oxidation. A similardisclosure as to the formation of tolualdehyde is made in British Pat.No. 1,485,816. Japanese Publication No. J5 1146-430 based on JapanesePatent Application No. 070587 discloses the formation of tolualdehydefrom the reaction of toluene and carbon monoxide in the presence oftrifluoromethanesulfonic acid (often referred to as triflic acid) in ananhydrous state or in combination with a Lewis acid.

The use of compounds of rhodium and copper together as catalysts,likewise, is known in the art. For example, Mimoun, et al. in J. Am.Chem. Soc. 100:17 (1978), 5437 disclose the selective oxidation ofterminal olefins to methyl ketones by oxygen in the presence of rhodiumchloride and cupric nitrate or cupric perchlorate; the copper compoundenhances the catalytic efficiency of the rhodium trichloride in theconversion of 1-hexene to 2-hexanone. U.S. Pat. Nos. 4,237,071 and4,237,331 disclose the use of a catalyst comprising compounds ofpalladium and copper and a surfactant for the oxidation of olefins toketones. U.S. Pat. No. 4,262,141 discloses hydroformylation of olefinsusing rhodium carbonyl complexes containing tertiary phosphine ligandsin the presence of a compound of copper, silver or zinc.

The addition of copper salts to improve the conversion of synthesis gas(largely carbon monoxide and hydrogen) to polyhydric alcohols in thepresence of a rhodium carbonyl catalyst is known from U.S. Pat. No.4,199,521. Copper is said to remove the sulfide contaminant from thesynthesis gas.

British Pat. No. 1,164,561 discloses the preparation of carbonylcompounds, including carboxylic acids, by reacting an organometalliccompound of a Group VIII noble metal (Ru, Rh, Pd, Os, Ir, Pt) withcarbon monoxide in a suitable solvent. Water is needed to form acarboxylic acid. Toluene is converted to toluic acids, with 94-96%selectivity to the para isomer. Use of a redox system, particularlycopper salts and air, to re-oxidize the Group VIII metal in-situ andincrease catalyst efficiency, is disclosed.

U.S. Pat. No. 4,281,174 discloses the preparation of dialkyl oxalates byreacting an alcohol with a mixture of carbon monoxide and oxygen in thepresence of a palladium complex, a quinone and a redox agent which caninclude a copper compound.

U.S. Pat. No. 4,076,949 discloses an oxidative carbonylation of alcoholin the presence of a catalytic mixture of (a) a palladium, rhodium,platinum, copper or cadmium salt; (b) an amine; (c) an oxidant compoundcomprising a salt of Cu⁺¹, Cu⁺², Fe⁺² or Fe⁺³ ; and (d) an ammonium orsubstituted ammonium salt or acid with a counterion other than halide.

It is an object of this invention to provide a catalytic liquid phaseprocess for producing toluic acids from toluene. A further object is toprovide such a process whereby at least 50 mol % of the toluic acidsproduced is p-toluic acid. Still another object is to provide such aprocess whereby the yields of the p-isomer are high. Other objects willbecome apparent hereinafter.

DISCLOSURE OF INVENTION

For further comprehension of the invention, and of the objects andadvantages thereof, reference may be made to the following descriptionand to the appended claims in which the various novel features of theinvention are more particularly set forth.

This invention provides a process for preparing toluic acid, at least 50mol % of which is the p-isomer, by reacting toluene, carbon monoxide andoxygen in the presence of a sulfur oxy-acid salt of rhodium or iridium,a cupric salt of a sulfur oxy-acid, and a sulfur oxy-acid having aHammett acidity (-H_(o)) of greater than 7. More particularly, theinvention resides in the process for preparing toluic acid, at least 50mol % of which is p-toluic acid, by contacting and reacting toluene,carbon monoxide, oxygen and the catalyst ingredients consistingessentially of

(a) a compound of rhodium or iridium;

(b) a sulfur oxy-acid or a Group Ia or IIa metal salt of a sulfuroxy-acid;

(c) a sulfur oxy-acid or sulfur oxy-acid mixture having a Hammettacidity value (-H_(o)) of greater than 7.0; and

(d) a cupric salt of a sulfur oxy-acid, preferably of a strong sulfuroxy-acid, for example, sulfuric acid or a sulfonic acid;

said catalyst ingredients containing 0.3-30 mol % of (a) and 70-99.7 mol% of (b+c+d), with the molar ratios (b/a) and (c/a) each being at least2, preferably at least 3, more preferably at least 4, the molar ratio(d/a) being at least 0.5, preferably at least 4, more preferably atleast 8, and recovering toluic acid.

Included under (c) are strong sulfur oxyacids such as, for example,sulfuric acid (-H_(o) of 11), oleum and certain sulfonic acids which arealso suitable for use under (b). Although not wishing to be bound bythis explanation, it is thought that the active catalyst for theoxidative carbonylation reaction consists of one or more ionic speciesof sulfate or sulfonate of rhodium or iridium and copper, formed by thepartial or complete replacement of the anions or ligands of the startingmetal compounds with anions from a sulfur oxy-acid or salt thereof, inthe presence of strong acid of -H_(o) greater than 7.0. Evidence for theformation of ionic sulfonates in the reaction of a rhodium compound witha sulfur oxyacid is provided hereinafter in Example 11. Further evidenceis provided in the Procedure for Catalyst Preparation using Nafion®Perfluorosulfonic Acid Resin described below wherein a reaction betweenrhodium nitrate, copper nitrate and the polymeric sulfonic acid isfollowed by titration of the liberated nitric acid and by analysis ofrhodium and copper chemically bound to the polymer.

The metal compound which is used as catalyst ingredient (a) can be anyrhodium or iridium compound capable of combining chemically with asulfur oxyacid or its metal salt. Examples of such compounds includerhodium acetate, trifluoroacetate, chloride and nitrate, the rhodiumcarbonyls Rh₆ (CO)₁₆ and RhH(CO)(Pφ₃)₃, where φ is phenyl, and iridiumchloride. Examples of suitable sulfur oxy-acids, catalyst component (b),include sulfuric acid; oleum; fluorosulfonic acid; α-fluorosulfonicacids, including trifluoromethanesulfonic acid (triflic acid),perfluorooctanesulfonic acid, and CF₃ CF₂ OCF₂ CF(CF₃)OCF₂ CF₂ SO₃ H(perfluoro-4-methyl-3,6-dioxaoctanesulfonic acid); methanesulfonic acid;benzenesulfonic acid; and p-toluenesulfonic acid. Examples of sulfuroxy-acids which are suitable for use as catalyst component (c) includethe above sulfur oxy-acids which have an -H_(o) of greater than 7.0.

Preferred catalysts in the process of this invention provide toluic acidcomprised of at least 70 mol % p-toluic acid; especially preferredcatalysts provide toluic acid comprisd of at least 85 mol % p-toluicacid. Preferred catalysts, in addition to the preferences noted above,include those wherein catalyst ingredients (b) and (c) are the same andconsist of a sulfur oxy-acid having an -H_(o) greater than 7.0. The mostpreferred catalysts herein include those wherein the molar ratios (c/a)and (d/a) are at least 4 and 8, respectively, ingredient (a) is acompound of rhodium or iridium and the sulfur oxy-acid (c), andingredients (b) and (c) are the same.

Sufficiently strong, that is, having an -H_(o) of greater than 7.0,polymeric sulfonic acids also can be used in the process of theinvention. Such acids are comprised of polymeric materials havingsulfonic acid groups attached to the polymer structure. Representativeof such a sulfonic acid is a perfluorinated polymeric sulfonic acid.Nafion® Perfluorosulfonic Acid Products represent commercially availablematerials of this type. The use of Nafion® as a strong acid is describedin J. Org. Chem., 42, 4187 (1977) and 43, 3142 and 3147 (1978) in aseries of papers by Olah et al. and Kaspi et al. and entitled"Heterogeneous Catalysis By Solid Superacids." It should be understoodthat the polymeric sulfonic acids useful in this invention normallyprovide catalyst ingredients (b) and (c). If, however, the sulfonic acidsites in the polymer have been largely or completely neutralized, i.e.,converted to the salt form by the addition of a salt or hydroxide of aGroup Ia or IIa metal, only catalyst ingredient (b) is provided by thepolymer and a strong acid ingredient (c) must be added to obtain anoperable catalyst. It will be obvious to one skilled in the art thatwhen at least 0.5 mol % of the sulfonic acid or sulfonate salt sites inthe polymer have reacted with the catalytically active rhodium oriridium ions, catalyst ingredient (a) is also provided by the polymer.Similarly, catalyst ingredient (d) can be provided by the polymer ifsufficient polymer sites have reacted with the catalytically activecopper. Catalysts prepared herein from a polymeric sulfonic acid arereferred to as heterogeneous catalysts. Those prepared herein from thenonpolymeric sulfonic acid are referred to as homogeneous catalysts.

Included in this invention are perfluorinated polymeric sulfonic acidshaving, based on the sulfonic acid groups, about 5 to 98.5 mol % ofhydrogen ions and 1.5 to about 95 mol % of rhodium or iridium and cupricions, the molar ratio of cupric ions to rhodium or iridium ions being atleast 0.5. Preferred polymeric sulfonic acids have 50 to 98.5 mol % ofhydrogen ions and 1.5 to 50 mol % of the rhodium or iridium and copperions, the molar ratio of cupric ions to rhodium or iridium ions being atleast 4, more preferably at least 8. Also included in this invention areperfluorinated polymeric sulfonate salts having, based on the sulfonategroups, about 5 to 98.5 mol % of Group Ia or Group IIa metal ions and1.5 to about 95 mol % of rhodium or iridium and cupric ions, the molarratio of cupric ions to rhodium or iridium ions being at least 0.5.

The process of the invention is carried out at 110°-250° C., preferably130°-200° C. At below 110° C. the reaction proceeds, but at slow rates.There is little, if any, advantage in operating the process above 250°C. Particularly if any catalyst component is a thermally unstablematerial, for example, as are some polymeric sulfonic acids, the upperlimit of reaction temperature must be selected accordingly.

Although the reaction pressure is not critical to the process of theinvention, generally it should be at least 500 psi (3.45 MPa). The upperlimit of pressure is usually governed by the cost of the equipmentneeded to contain the reactant materials.

Preferably, in order to avoid the use and handling of an explosivereaction mixture, the amount of oxygen introduced into the system shouldnot exceed 7.5 mol % of the combined amounts of carbon monoxide andoxygen in the system. If the reaction is carried out in a batch typeoperation, for example, in an autoclave, it may be desirable, in orderto maintain the lowest possible level of oxygen, to introduce theinitial charge of toluene and carbon monoxide before adding the oxygen.Carbon monoxide can then be added subsequently in such amounts as isnecessary to maintain the desired reaction pressure as carbonylationtakes place.

As is already evident from the above description, the reaction can becarried out in a batchwise or continuous mode of operation in a systemwhich can be either homogeneous or heterogeneous, depending on whetheror not the catalyst is soluble in the reaction medium. Although asolvent or liquid medium which is inert to oxidative carbonylation canbe present during the reaction, it is not necessary in the process ofthe invention since the toluene itself serves as a solvent or liquidmedium. Workup of the toluic acid from the reaction mixture can becarried out by conventional means. Hetergeneous catalyst can be removedby filtration of the reaction mixture. When a soluble catalyst is used,that is, when the system is homogeneous, the reaction mixture can bediluted with methylene chloride and extracted with aqueous sodiumchloride, after which the methylene chloride layer can be evaporated torecover the toluic acid.

In the following examples, the toluic acids which were produced wereconverted to trimethylsilyl esters by conventional techniques and thenanalyzed by means of standard gas chromatographic procedures. All of theoxidative carbonylation examples (Examples 1 to 11) and comparativeexperiments (Experiments S1 to S17) were carried out at 150° C. and 27.6MPa pressure except for Example 7 and Experiment S4 which were carriedout at 13.8 MPa pressure and Experiment S16 which was carried out at180° C.

Procedure for Catalyst Preparation Using Nafion® Perfluorosulfonic AcidResin

The heterogeneous catalysts were prepared by stirring, preferably atabout 40° to 95° C., and aqueous solution of a soluble compound ofrhodium or iridium and cupric copper (for example, the nitrate orchloride) with Nafion® (H⁺) (of equivalent weight 1100) either until thesupernatant of the resultant slurry was colorless or for such time aswas necessary to convert the desired number of acidic sites in theNafion® (H⁺) to the cupric and rhodium or iridium metal salts. Theformation of the metal salts can be followed by titrating the acid (forexample, nitric acid or hydrochloric acid) liberated in the supernatantof the slurry. A specific example of the procedure follows.

Twenty-two g of Nafion® (H⁺) containing 20 m equiv of sulfonic acidgroups in 450 ml of H₂ O was stirred with 0.54 g of Rh(NO₃)₃.2H₂ O (1.66mmoles Rh) and Cu(NO₃)₂.3H₂ O (1.65 mmoles of Cu) at 95° C. for about 27h. The resultant slurry was filtered and the orange resin was dried in avacuum oven for about 3 h at about 100° C. The filtrate was titrated forliberated nitric acid (7.4 mmoles of HNO₃). The catalyst thus preparedcontains ##EQU1## The mol % of rhodium in catalyst ingredient (a), ascalculated by the formula given below for Examples 1-10, is ##EQU2## Themol % of copper in catalyst ingredient (d), similarly calculated, is##EQU3##

Nafion® (H⁺) may be converted to a salt form, for example, the Na salt,by a similar procedure wherein the resin is treated with an aqueoussolution of sodium chloride or sodium nitrate. The salt form may befurther treated with water-soluble rhodium or iridium and cupriccompounds to replace the desired number of Na ions with ions of rhodiumor iridium and copper.

Alternatively, Nafion® (H⁺) may be converted substantially to a salt ofrhodium or iridium and copper by either of the above techniques, and anappropriate strong acid may be added to provide the necessary catalystingredients (b) and/or (c), as discussed above.

Procedure for Shaker Tube Experiment with Heterogeneous Catalyst FromNafion®

In a typical experiment, a shaker tube was flushed with N₂, charged withthe catalyst prepared as described above, cooled, evacuated and chargedwith 80 to 120 ml of toluene. The tube was sealed and heated to reactiontemperature. Carbon monoxide, then oxygen, and then more carbon monoxidewas introduced into the tube until the desired pressure was reached. Themol percent of oxygen was 7.5. During the reaction time of two hours,the tube was repressurized with carbon monoxide as necessary to maintainpressure during carbonylation. After the tube was discharged, thecatalyst was removed by filtration and the filtrate was analyzed fortoluic acids.

Procedure for Shaker Tube Experiment With Homogeneous (Soluble) Catalyst

In a typical experiment, a shaker tube (Hastelloy-C or tantalum) isflushed with N₂, charged with (a) an approprite rhodium or iridiumcompound, (b) a suitable sulfur oxy-acid or metal salt thereof, (c) asuitable sulfur oxy-acid or sulfur oxy-acid mixture having an -H_(o) ofgreater than 7.0, (d) a cupric salt, and (e) 80 ml of toluene, cooledand evacuated. Alternatively, the rhodium or iridium compound can bereacted separately with excess sulfur oxy-acid or metal salt thereof andthen charged to the shaker tube in place of the first two ingredientsdescribed above. After being charged the tube is sealed and heated toreaction temperature. Carbon monoxide, then oxygen, and then more carbonmonoxide is introduced into the tube until the desired pressure isreached. The mol % of oxygen in the tube is no greater than 7.5. Duringthe reaction time of two hours, the tube is repressurized with carbonmonoxide as necessary to maintain pressure during carbonylation.Alternatively, the shaker tube is pressurized with a gaseous mixture ofoxygen in carbon monoxide (mol % of oxygen is 3%) and then the mol % ofoxygen is increased to 7.5% by the addition of oxygen. During thereaction time of two hours the tube is repressurized with carbonmonoxide/oxygen mixture (3 mol % oxygen). After reaction the tube isdischarged of the liquid contents and the recovered solution is dilutedwith CH₂ Cl₂ and extracted with saturated aqueous NaCl solution. Theorganic phase is dried over MgSO₄, concentrated to a small volume, andthen analyzed for toluic acids.

EXAMPLES 1-10

These examples represent various embodiments of the process of theinvention, carried out using the procedures outlined above. Appropriatedata for the examples using the homogeneous catalyst are summarized inTable 1, for the examples using the heterogeneous catalyst, in Table 2.At the end of each table are provided data relative to experimentalshowing (S) which were carried out to compare the process of theinvention as claimed herein with similar processes outside theinvention.

For the homogeneous systems, Experiments S1 to S6 (Table 1), show that,in the absence of catalyst ingredient (d), selectivity to p-toluic acidis maintained at a high level, but the yield of p-toluic acid isrelatively low, unlike the present process which provides high yields ofthe p-isomer. Experiments S7 and S8 show that reduced forms of copper(Cu⁺ and Cu metal) destroy catalyst effectiveness so that no toluicacids are produced. Experiments S9 shows that the use of cupric salt ofa weak, nonsulfur-containing acid (acetic acid) fails to increasep-toluic acid yield and reduces selectively to the p-isomer. ExperimentsS10 to S14, described separately below, show the ineffectiveness ofother metal salts as replacements for cupric salts.

For the heterogeneous systems, Experiment S15 (Table 2) shows that asubstantially reduced yield of p-toluic acid is obtained in the absenceof catalyst ingredient (d). Experiment S16 shows that the presence ofcatalyst ingredient (a) is essential for catalytic activity.

In the following tables (Table 1, column 4; Table 2, columns 4, 5), thedifference between the mol % metal (rhodium or iridium+copper, i.e. thetotal amount of catalyst ingredients (a) and (d)) and 100 mol %represents the mol % of catalyst ingredients (b)+(c). In Examples 1-4and 6-10 (Tables 1 and 2), ingredients (b) and (c) are provided by thesame compound. In Example 5 (Table 1), mol % of ingredient (b), CF₃ SO₃Na, is shown.

In the tables the mol % metal (rhodium or iridium and copper) shown iscalculated using the formulae: ##EQU4## where (a), (b), (c), and (d) arethe catalyst ingredients defined above, n is the number of gram atoms ofrhodium or iridium per mol of (a) and m is the number of gram atoms ofcopper per mol of (d).

Experiments S10 to S12 and Example 3 are similar, the difference beingthat the cupric salt (of Example 3) was replaced with Mn(O₃ SCF₃)₂,NiSO₄ and Fe (SO₄)₃ in Experiments S10 to S12, respectively. Mol %manganese, nickel and iron was 28.9, 31.6, and 30.3, respectively; mol %rhodium was 1.4 in each experiment. Experiments S13 and S14 were similarto Example 9 except that the cupric salt was replaced with Co(O₃ SCF₃)₂and Ce(SO₄)₂, respectively. Mol % cobalt and cerium was 28.2 and 44.7,respectively; mol % rhodium was 2.8 in Experiment S13 and 2.2 inExperiment S14. In Experiments S10 to S14, selectivity to p-toluic acidwas in the range 85 to 93 mol %, but the amount of p-toluic acidproduced varied from nearly zero (cerium) to 2.6×10⁻ 3 mol (manganese),indicating no significant improvement in p-isomer yield over thatachieved with rhodium alone.

                  TABLE 1                                                         ______________________________________                                        Homogeneous Catalyst                                                                                               p-                                       Catalyst Components                                                                             Mol                Toluic                                   Ex.          Amount   %      Distribution                                                                            Acid                                   or           (mol     Me-    (mol %)   (mol                                   Exp. Compound    × 10.sup.3)                                                                      tal  o   m    p    × 10.sup.3)                ______________________________________                                        1    Rh.sub.6 (CO).sub.16                                                                      0.19     1.7  0.6 3.9  95.4 14.8                                  CuSO.sub.4  20.6     30.9                                                     CF.sub.3 SO.sub.3 H                                                                       45.1                                                         2    Rh(NO.sub.3).sub.3.2H.sub.2 O                                                             0.92     1.1  2   7    91   13.3                                  CuSO.sub.4  41.4     47.4                                                     CF.sub.3 SO.sub.3 H                                                                       45.1                                                         3    Rh(NO.sub.3).sub.3.2H.sub.2 O                                                             0.92     1.4  2   9    89   7.9                                   CuSO.sub.4  20.6     31.1                                                     CF.sub.3 SO.sub.3 H                                                                       45.1                                                         4    Rh(NO.sub.3).sub.3.2H.sub.2 O                                                             0.92     1.7  2.5 8.5  89   7.8                                   Cu(O.sub.3 SCF.sub.3).sub.2                                                               9.1      16.5                                                     CF.sub.3 SO.sub.3 H                                                                       45.1                                                         5    Rh(NO.sub.3).sub.3.2H.sub.2 O                                                             0.92     1.3  3   7    90   4                                     Cu(O.sub.3 SCF.sub.3).sub.2                                                               18.3     26.1                                                     NaO.sub.3 SCF.sub.3                                                                       5.8      8.3                                                      CF.sub.3 SO.sub.3 H                                                                       45.1                                                         6    Rh(NO.sub.3).sub.3.2H.sub.2 O                                                             0.92     2.7  0.8 7.8  91.4 5.9                                   Cu(O.sub.3 SφCH.sub.3).sub.2                                                          9.85     28.9                                                     CH.sub.3 φSO.sub.3 H                                                                  23.3                                                         7    Rh(NO.sub.3).sub.3.2H.sub.2 O                                                             0.92     1.6  0.8 6.5  92.7 3.9                                   Cu(O.sub.3 SφCH.sub.3).sub.2                                                          9.85     17.2                                                     CH.sub.3 φSO.sub.3 H                                                                  46.5                                                         8    IrCl.sub.3  1.0      1.1  3   14   83   9.7                                   CuSO.sub.4  41.3     47.3                                                     CF.sub.3 SO.sub.3 H                                                                       45.1                                                         9    Rh(NO.sub.3).sub.3.2H.sub.2 O                                                             0.92     2.9  1   9    90   6.2                                   Cu(O.sub.3 SCF.sub.3).sub.2                                                               8.3      26.2                                                     CF.sub.3 SO.sub.3 H                                                                       22.5                                                         S1   Rh(NO.sub.3).sub.3.2H.sub.2 O                                                             0.92     1.8  2   9    89   1.5                                   NaO.sub.3 SCF.sub.3                                                                       5.8      11.1                                                     CF.sub.3 SO.sub.3 H                                                                       45.1                                                         S2   Rh(NO.sub.3).sub.3.2H.sub.2 O                                                             0.92     1.9  2.2 6.4  91.4 2.5                                   CF.sub.3 SO.sub.3 H                                                                       45.1                                                         S3   Rh(NO.sub.3).sub.3.2H.sub.2 O                                                             0.92     3.8  1   6    93   1.2                                   CH.sub.3 φSO.sub.3 H                                                                  23.3                                                         S4   Rh(NO.sub.3).sub.3.2H.sub.2 O                                                             0.92     1.9  0.9 5.5  93.6 1.3                                   CH.sub.3 φSO.sub.3 H                                                                  46.5                                                         S5   IrCl.sub.3  1.0      2.2  1.3 12.4 86.3 2.5                                   CF.sub.3 SO.sub.3 H                                                                       45.1                                                         S6   Rh(NO.sub.3).sub.3.2H.sub.2 O                                                             0.92     3.9  1.2 6.4  92.3 1.8                                   CF.sub.3 SO.sub.3 H                                                                       22.5                                                         S7   Rh(NO.sub.3).sub.3.2H.sub.2 O                                                             0.92     1.0  0   0    0    0                                     Cu.sub.2 O  41.7     47.5                                                     CF.sub.3 SO.sub.3 H                                                                       45.1                                                         S8   Rh(NO.sub.3).sub.3.2H.sub.2 O                                                             0.92     0.74 0   0    0    0                                     Cu          78.1     62.9                                                     CF.sub.3 SO.sub.3 H                                                                       45.1                                                         S9   Rh(NO.sub.3).sub.3.2H.sub.2 O                                                             0.92     1.1  6.2 31   62.8 2.4                                   Cu(OCOCH.sub.3).sub.2                                                                     36.3     44.1                                                     CF.sub.3 SO.sub.3 H                                                                       45.1                                                         ______________________________________                                    

                  TABLE 2                                                         ______________________________________                                        Heterogeneous Catalyst                                                             Pre-                                  p-                                      pared                        Isomer   Toluic                             Ex.  Cata-   Nafion ®         Distri.  Acid                               or   lyst    Resin    Mol % Mol % (mol %)  (mol                               Exp. (g)     Form     Rh    Cu    o   m    p   × 10.sup.3)              ______________________________________                                        10   4       H.sup.+  7.1   7.1   2   11   87  0.2                            S15  4       H.sup.+  14.5  0     1.5 12.5 86  0.08                           S16  3       H.sup.+  0     19.1  0   0     0  0                              ______________________________________                                    

EXAMPLE 11

A sample of Rh(OH)₃.H₂ O, prepared from RhCl₃.3H₂ O by the procedure ofBasolo, Inorganic Syntheses, VII, page 214, was reacted without externalheating with a 3:1 molar excess of trifluoromethanesulfonic acid.Unreacted acid was distilled off under reduced pressure and areddish-brown solid was recovered. Infrared analysis of the solid showedcharacteristic bands at 1250 cm⁻¹, 1176 cm⁻¹ and 1030 cm⁻¹, closelysimilar to the trifluoromethanesulfonate ion (CF₃ SO₃ ⁻) bands observedin various metal salts of trifluoromethanesulfonic acid by Gramstad andHaszeldine, J. Chem. Soc., 173 (1956), Haszeldine & Kidd, J. Chem. Soc.,4228 (1954), and Batchelor et al., Inorg. Chem., 16, 1414 (1977).

The rhodium salt, prepared as described above, was used as ingredient(a) in a homogeneous catalyst of this invention. The catalyst was usedto prepare toluic acid according to the previously described shaker tubeprocedure for homogeneous systems. The results are given in Table 3.Also shown in Table 3 are the results of comparative Experiment S17which is outside this invention. The comparison experiment has beenincluded to show the effect of eliminating catalyst ingredient (d).

                  TABLE 3                                                         ______________________________________                                        Homogeneous Catalyst                                                                                               p-                                       Catalyst Components       Isomer     Toluic                                   Ex.          Amount           Distri.  Acid                                   or           (mol     Mol %   (mol %)  (mol                                   Exp. Compound    × 10.sup.3)                                                                      Metal o   m    p   × 10.sup.3)                ______________________________________                                        11   Rh(O.sub.3 SCF.sub.3).sub.3                                                               0.55     0.9   1.1 9.9  89  29.3                                  CuSO.sub.4  37.5     61.9                                                     CF.sub.3 SO.sub.3 H                                                                       22.5                                                         S17  Rh(O.sub.3 SCF.sub.3).sub.3                                                               0.55     2.4   2   9    89  1.8                                   CF.sub.3 SO.sub.3 H                                                                       22.5                                                         ______________________________________                                    

Best Mode For Carrying Out The Invention

The best mode for carrying out the process of the invention is believedto be demonstrated by Examples 11, 1, 2 and 10.

Industrial Applicability

Toluic acid, particularly p-toluic acid, is an important intermediate inthe preparation of terephthalic acid which is used in the manufacture offiber-forming polyesters.

Although the preferred embodiments of the invention have beenillustrated and described, it is to be understood that there is nointent to limit the invention to the precise construction hereindisclosed and that the right is reserved to all changes andmodifications within the scope of the invention as defined in theappended claims.

I claim:
 1. Perfluorinated polymeric sulfonic acid having, based on thesulfonic acid groups, about 5 to 98.5 mol % of hydrogen ions and 1.5 toabout 95 mol % of rhodium or iridium and cupric ions, the molar ratio ofcupric ions to rhodium or iridium ions being at least 0.5. 2.Perfluorinated polymeric sulfonic acid having, based on the sulfonicacid groups, 50 to 98.5 mol % of hydrogen ions and 1.5 to 50 mol % ofrhodium or iridium and cupric ions, the molar ratio of cupric ions torhodium or iridium ions being at least
 4. 3. Perfluorinated polymericsulfonate salt having, based on the sulfonate groups, about 5 to 98.5mol % of Group Ia or Group IIa metal ions and 1.5 to about 95 mol % ofrhodium or iridium and cupric ions, the molar ratio of cupric ions torhodium or iridium ions being at least 0.5.